Music on hold randomisation issue

I'm currently having a strange issue with the random hold music feature...or lack thereof. I understand v11 is going to have a whole bunch more MOH options but I'd really rather get this fixed on v10 first. The box itself is a virtual machine (Hyper-V) running 2008 Server SP2 with a 3CX v10 SP6 installation.

I've set up 5 audio tracks in the MOH section, with the "Control behaviour" option ticked with randomisation of MOH per call. Incoming calls hit the digital receptionist, where they make a selection to go to their destination of choice (they happen to be ring groups.) The call goes on hold as it transfers to the group, with a random music track. The call is picked up and chat occurs, but if the call is then placed on hold again the random music choice will play for 1-2 seconds, pause briefly then start playing the first song selected in the MOH settings. Every time.

At first I thought it was a call queue issue, as there are separate MOH options per queue available in addition to the system-wide settings. So, I pulled all the queues and made them all ring groups instead. The behaviour did not change.